The disclosed embodiments relate to a method of cutting out a panoply of parts. The method enables one to automatically and optimally determine a cutting order for the parts.
The disclosed embodiments are applicable in the area of technology of fabrication of industrial parts, particularly in the aeronautics industry, in instances where the parts to be produced have different sizes and shapes, and the panoplies of parts may be defined in response to time-variant needs, in a manufacturing organization employing “just in time” scheduling which necessitates time efficiencies as well as economic efficiencies.
Under current concepts, in fabricating parts having regular or irregular shapes, by means of bending, stamping, or deep drawing, one first cuts out blanks corresponding to the parts, from a plate or plates, typically comprised of a metal alloy, a plastic, or a composite. The situation often presents itself where it is desired to cut out a number of blanks of very different shapes from a single plate or stack of plates. Hereinafter, the term “part” will be understood to mean a blank intended to be used for fabrication of a part.
The term “interlacing” (in French, “imbrication”) is used to designate a process of establishment of an arrangement of parts with respect to each other starting with their geometric data, with consideration of the path (progression) of the cutting tool to be used, with aim of optimizing the ratio between the area of the parts and the area of the plate, so as to reduce the amount of scrap.
The term “panoply of parts” is used to designate the totality of parts positioned on a given plate.
At the conclusion of the “interlacing” process, each part is represented by an outline (or “box”) which surrounds it, particularly the center point of its outline, and by its orientation in the set of coordinates adopted for the panoply; and each part is associated with a fabrication path.
Before each cutting-out operation, it is necessary to determine an order of cutting out of the parts in the panoply, wherewith each part is assigned a number, and the cutting order is input into a program associated with the control system of the cutting apparatus. The cutting tool guided by this control system cuts out the parts in conformance with this established cutting order.
In current practice, this step of establishing the cutting order is performed manually by an experienced preparer.
The establishment of the cutting order is a very important step in the process, because it governs the path of the tool during the cutting. It has an appreciable influence on the accuracy of the cutting, thus on the quality of the parts and on the yield and efficiency of the cutting operation. As the cutting out of the panoply progresses, the parts which have been cut out are no longer attached to the panoply, wherewith zones without material (voids) are left in the plate, giving rise to “skeleton” regions. Prior to being cut out, parts are disposed near such void-containing zones, exposing them to unstable situations, in that they receive reduced support from the material. This “instability” during cutting causes reduced cutting accuracy, which may detract from the quality of the parts. The cutting order is particularly critical if the plate is not well held on the table of the cutting apparatus, and particularly in the case of a stack of plates. At the same time, cutting of a stack of plates with minimum holding is a process which offers maximum flexibility and is thus well suited for use in “just in time” fabrication schemes. It is fundamentally important that the preparer be able to provide a judicious choice of the cutting order in order to meet the criteria of success in the fabrication of the ultimate parts.
If the cutting order is not correctly established, disadvantageous or even dangerous shifting may occur which can adversely affect the quality of the parts cut out.
Another technical drawback of manual establishment of the cutting order is the time which the preparer consumes in the task of establishing the order. In the “just in time” production environment of the aeronautics manufacturing industry, the composition of a panoply of parts will depend on current needs (which may vary); a given panoply will not be identical to the prior one. The preparer must perform a new optimization each time the configuration of the panoply changes.